Process for treating steel



July 3, 1962l l s. R. HEMMETER PRocEss FOR TREA'rNG STEEL Filed Feb,4 2. 1.960

l :July 3,1962 s, R. HEMMETER( 3,042,556

' PROCESS FOR TREATING STEEL Filed' Ffeb 2, 1960' l V I 5 Sheets-Sheet 6. R. HEMMTER 3,042,556 f APROCESS FOR TREATING STEEL July-3, 1962 5' sheets-sheet s Filed Feb. 2, 1960 @wml m HQ... am 1N. mw wf la w M N G w w M WAY NW W s s w m M m y Awal-wey.

.July 3,4 `1962 piled 'Feb. 2V. 4195o I G. R. HEMMETER 3,042,556 lacxizzssv FOR 'fam-'rms STEEL I 5 `Sheets-Sheet 4 i600 1650' I' on 1750 /soo f9.5@

` Arder-nay- 3,042,556 PROCESS FOR TREATING STEEL George R. Hernmcter, Fort Wayne, Ind., assignor to General -Ele'ctric Company, a corporationof New York Filed Feb. 2, 1960, Ser. No. 6,190

4 Claims. (Cl..148111) This invention relates toa process for treating electrical steel, and in particular, to a process which isadaptable for a production line type of operation for manu- `facturing laminations and core components for dyna- 1 moelectric machines 4from a critically. strained silicon .'steel strip.V This application is a .continuation-impart of rny application Serial Number 667,947, tiled June 25, 1957, now abandoned. v

Conventional methods of producing laminations and core components have not been satisfactory from an economic standpoint to adapt to a production line operaadverse elect upon magnetic or mechanical properties, or result in a distortion of the strip be eliminated. A general object of the present invention is to provide 1 yan improved method for magnetically 'annealing critically strained silicon steel strip.

It is another object of the invention'to provide an improved method of magnetic annealing that is readily adaptable to a production line manufacturing operation.

tion. A principal drawback has been the comparativelyY long periods oftime'require'd to accomplish magnetic vannealing of the fabricated parts, Heretofore, it has been the practice in industryv to carry out the magnetic. anneal of critically strained silicon steel strips in roller hearth furnaces requiring a semibatch type of operation. There is therefore a need in industry for a magnetic annealing treatment with a time rate ofrelatively short duration that will bring about the requisite change in grain structure necessary `for improving the magnetic quality and thereby make it practicable to produce laminations and core components on a continuous production line basis.

A further object of the invention is to provide au improved process of treating an electrical steel strip in which the magnetic annealing of the steel strip can be accomplished in relatively short periods of. time to produce a .steel strip of improved magnetic quality.

In accordance with the invention, aprocess'of treat- `ing a silicon steel strip is provided wherein it is conditioned so that a minimum core loss can be achieved by an annealing treatment which requires a total isothermal heating time ranging from l5 seconds to 15 minutes. A silicon steel strip of a' thickness ranging fromI .05 to .125 inchis cold rolled to an intermediate thickness l which requires a predetermined elongation from 2 per- A typical critically strained silicon steel strip that can be 4employed in the practice of the invention is described v in the McKnight Patent4 2,738,295, granted on March `13, 1956. The improved magnetic characteristics of such critically strained silicon steels-when'subiectedto a magnetic anneal are well known.

A principal'purpose 'of the magnetic annealing treatment is to obtain a grain orientationand size which will improvethe magnetic quality of the steel and the improved magnetic'properties are not obtained in this steel until thecornpletely new grain structure is formed. It will be appreciated that an annealing treatment for mag- .netic properties'diifers from the conventional annealing methods' employed to improve mechanical properties of a steel, such as its ductility, since the improvement in the mechanical properties may not necessarily bring about the desired improvement in the magnetic quality of the steel. vIn the past, to produce the grain structure requif site :for minimum core losses, the .annealing time wasl vgenerally on the lorder of an hour or more at tempera-1.

` ture,4 and for this reason the magnetic annealing treatf. -ment was carried outvin large furnaces in a semiabatch type of operation.v It is therefore desirable that they magnetic annealing be accomplished in relatively shorter periods of time so that--a.heating means readilyadapt- -foregoing temperature range that produces a 100 percent grain response also produces the largest grain struccent to 12 percent elongation to bring the thickness down Y to desired final gauge.

After this cold reduction, the steel strip is subjected to a normalizing treatment and cooled. After this step,

the critically strained strip may be fabricated into the desired shape for the particular electrical application in which it is intended. The parts are then magnetically annealed at the minimum time ranging between 15 seconds and l5 minutes at a 'preselected isothermal annealingtemperature between 1650 degrees and 2100 degrees Fahrenheit that will result in a 100 percent grain rei vspouse or minimum' core loss.

Unexpectedly, it was found that for a fixed magneticV annealing time the lowest temperature within the ture and 'the lowest core loss obtainable at the fixed annealing time. Contrary to what might be expected, to carry out the magnetic annealing treatment at a higher temperature for the aforementioned fixed annealing `time produced a grain structure that provided an increased core loss. y Thus, for a xed predetermined annealing time a minimum core loss is obtained at approximately the same time that thelOO percent grain v' response is achieved at the lowest isothermal annealing able to a production line operation, such as induction heating, may lbe effectively employed. Thus, by making it possible to` utilize induction heating techniques and` the like the advantages of lower capital investment, reduced Hoor lspace, lower maintenance costs, decreased amounts. of handling and lower production costs can be realized. t

In the application of magnetic steels, it is also necessary -that consideration be given to the mechanical prop- 4erties ofthe steel during its processing. Generally, the

surface of the laminations fabricated from an electrical steel strip should be relatively smooth in order that a lhigh space factor may be obtained when the laminations are stacked.` In a critically strained electrical steel Strip, because of the deformation present in the strip, it is desirable that any residual stresses which might have an temperature required for the predetermined annealing time.l

As the term is used herein, percent grain response means that the microstructure of the material does not contain a matrix of'ne grained material, but one in which the ne grains have been consumed bythe larger growing grains as evidenced by an examination of representative photomicrographs of the material.

Further objects and advantages of this invention will become apparent and the invention will be better under-- stood by reference to the following description and the Y accompanying drawings in which:

l shows comparative curves illustrating the'variation m core loss with flux. density for a 2.85 percent silicon steel strip with a 4 percent elongation and for` the same steel with a l0 percent elongation, both annealed at a temperature of 1650 degrees Fahrenheit at xed annealing times of 1/2, 1, 2% and 5 minutes;

FIG. 2 shows comparative curves illustrating the vari- 'y ation in core loss with changes in flux density for a 2.85

percent silicon steel strip with a 4 percent elongation and for. the-same steel with a l0 percent elongation, both annealed at a temperature of 1750 degrees Fahrenheit at ixed annealing times of 1/2, l, 21/2 and 5 minutes;

' FIG. 3 shows comparative curves illustrating the core g loss versus temperature fora 2.85 percent silicon steel Patented July 3, 1962 'fa production line type of manufacturing operation. the past,`i t was considered necessary to heat the fabricated elementsv for relatively long periods at temperatures above stripr with a 4 percent elongation and for the same steel4 with. a l percent elongation for fixed annealing times of l., 1.2V2 and 5-minutcs;

FIG. 4 shows the curves illustrating reduction of core i loss plottedagainst temperature for a 3.06 percent silicon steel stripwith a 4 percent elongation for fixed ani 'uealing times of 1/2, 1, 2%., 5 and l0-minutes;

" FIG. -is a graph'settiug forth the percent grain recent elongation at different temperatures for fixed time @intervals ofl seconds, 30 seconds, l minute, 5 min- `utesand 15 minutestand "FlG..6 -is a-graph setting forth the average .grain'slze plotted against time and temperature foran annealed ,-1.5 percent 'silicon steel strip with va 4 percent elongation.

The silicon strip steel used in the practice of the invention ismade from ingots melted-in an open hearth or electric furnace'and preferably has a silicon contentbetween f percent silicon critically strained in the final cold re'ducspouse of a' 1 .5 percent silicon steel strip with a 4 per- 0.25 andv3.5 percent by weight anda manganese content between .20 and .40 percent by weight. Aluminum may be present in an amount between .02 and .60'percent by weight. It is preferable that the phosphorus and carbon content'be kep-t down below .05 percent. A maximum of .03 percent of sulphur may be present in the composition.

-An ingot having the desiredcomposition is'heated in a .'g soaking pit in the 'mill and hot rolled into s1abs`of the width-ofthe finished coil and of a thickness between 0.05

:and .125 inch, depending upon the final gauge towhich the steel strip will-ultimately be rolled. After the hot roll, fit is passed through a pickling bath to remove any scale producedr by'tl'ie hot rolling operation. The steel strip is then 'given a cold reductionto reduce'A the strip to an inter-v `rnediate thickness which will require a predetermined elongation vranging lfrom 2 to l2 percent to bring vthe strip down toits final desired gauge. The first mill pass or rst 1400 degrees 'Fahrenheit to relieve the stresses and achieve the requisite grain structure. Itwas. found'that the steels containing from .25 to 3.5

tion in accordance with the present invention can be annealed in relatively short intervals of time ranging from 15 seconds Ato 15- minutes. Further, it was found that a silicon steel processedfor a l() percent elongation, as compared with a 4 percent elongation,4 could be annealed in a shorter period of time or at a reduced annealing temperature. In either case, the time intervals involved are short enough to permit the annealing to befcarried out in a continuous production line type of operation. Further, it will be appreciated that additional advantages afforded by a lower temperature of magnetic annealing are that difficult'ies encountered with adjacent layers of laminations sticking can be minimized and savings in energy requirements4 due to the lower temperature can be realized.

The curves of FIG. 1 of the drawings illustrate the comparative effect of a 4 percent and a 10 percent elongation on core loss of the silicon steel strip at a temperature'of v165() degrees Fahrenheit. FIG. 2 illustrates the corresponding curves at a temperature of 1750 degrees Fahrencold reducti'onof the silicon st eel strip is of signcance in the practice of the present invention since it affects vthe second cold reduction step with which this invention is Amore particularly concerned and which,` as hereinafter will be more fully described,` is a'factor that' affects the l rate of the annealing treatment.v

After completion of the first mill pass or cold reduction,

to achieve a recrystall'ization. The normalizing temperature, as the term is u se'd herein, is the temperature equal to or above the recrystallization temperature for the particular silicon steel, which is required to achieve recrystallizationof the steel butv precludes substantial grain growth. f The temperature of recrystallization may vvary from 1500 to 1850 ldegrees Fahrenheit depending upon the specific vcomposition of the silicon steel strip. The time required f will vary from 2 to 8 minutes depending upon the gauge of the strip and the-temperature of the furnace.. The purpose of the normalizing treatment is to recrystallize the fragmented grains ofthe deformed steelv and produce a vsteel having a very'fine equiaxed grain structure. vThe normalized silicon steel strip is then subjected to a final cold pass or -cold'reduction to produce the final gauge ofthe strip. It willfbe appreciated that the hereinbefore described stepscan bevreadily carried out at the mill in accordance` with'the specifications of the electrical equipment manufacturer. In this condition, the steel strip is ready'for fabrication into'laminations and the like.

After fabrication by the manufacturer, the silicon steel hstrip has been subjected to a severe straining which results from the shearing, punching and stamping-operation the steel strip is givena normalizing treatment. The strip '1 is vpassed through a furnace for a sufficient length of time heit. AFror'n' these curves, it will be seen thatthesteel strips with the 10 percent elongation produced by the final mill pass are more responsive to annealing than the' strips with the 4 percent elongation. For the 2.85 percent silicon steel strips used, itwas found that at a temperature between 1600. and 1700 degrees Fahrenheit the response for the steel having the 10 percent elongation was live 'timesas fast as the identical strip with the 4 percent elongation. 4It will be seen from FIG. l that atl650 degrees Fahrenheit'all of the sample strips, which were subjected to a millpass producing the l0 percent elongation, are completely annealed as evidence by the close grouping ofi all the curves. However, the curves for the steel strip 5amples with the 4 percent elongation indicate that only'"the 5 minute annealing time has produced a desirable grain structure and acceptable magnetic quality. Further, it will be apparent that for annealingftimes as short as one- .half minute, a steel strip vwith 4 percent elongation requires a temperature of at least l`7 50 degrees Fahrenheit before a complete grain response can be obtained.

In the curves .of FIG.' 3, the magnetic annealing response of the 2.85 percent silicon steel strip, as it is affected by temperature, is graphically shown. However, it will be noted that values given are for a 'single flux dens- 'ity of 15 kilogausses From these curves, it can be-seen that atA 1500 degrees Fahrenheit the steel strips witha 10 percent elongation have already begun to be annealed as evidenced'by the reduction in core loss for the 21/2 and'5l However, the silicon steell minute fixed time intervals.

' strips with a 4 percent elongation show no signs of being lannealed at 1500 degrees Fahrenheit for any of the fixed time intervals. At the 1800, 1850 and 1900 degrees Fahrenheit temperature levels, there is no substantial change in Vcore loss.

- be seen from the curves of FIG. 3 that the minimum core losses occur at a relatively low temperature for each of the illustrated fixed time curves as indicated by temperavtures at the minimal points of the curves. This prolonged heating above the temperature which correspondsl to the minimum core loss will result in an increased core loss. Thus, for thestrip with a l0 percent elongation the minimum core loss occurs at 1600 degrees for a fixed annealing period' of 21/2 minutes. If the magnetic anneal is carried out at 1800 degrees Fahrenheit for the 2% minutes performed upon the strip. Heretofore, it has not been considered possible to'anneal such silicon steel strips in 'relatively short intervals of time or to obtain the requisite grain structure required in steels of high magnetic quality that would make it possible to carry out the annealing in terials. The effect of the elongation 'produced by the final rnill pass is to shift the group of curves for a specific Contrary to what might be expected, it will elongation to the left, as viewed in FIG. 3, as the elongaquired to effect the magnetic anneal treatment. If such an y advantage is not of a significant factor, by increasing the annealing temperature, the annealing time can be reduced with a resultant increase in productive output.

The silicon steel strips'used to obtainthe data for the curves of FIGS. 1,'2 and 3 wereof the following composition as determined by chemical analysis.

Constituent: l Percent by 'weight Silicon 2.85 Carbon .024

`Aluminum .'3 Manganese .290 Phosphorus .0l Sulphur .024 Nickel .06 Copper .07 Tin .01

. 6 perature at fixed times for a silicon steel having the following analysis.

Constituent: Percent by weight Silicon 3.06 Carbon i .025 Aluminum .26 Manganese .33 Phosphorus .008 Sulphur .025 Nickel .13 Copper .071 Tin .011

A steel strip of the foregoing composition was given a final mill pass which produced a 4 percent elongation at a nal gauge of .025 inch. In order to obtain the data for the purpose of FIG. 4, rectangular laminations 1% inch wide and 4 inches long were cut with the longer dimension in the rolling direction. The strips were properly identified and were subjected to an annealing treatment for xed times of 1/2, 21/2, 5 and 10 minutes at 50 degree temperature intervals of from 1500degrees t0 1900 degrees Fahrenheit. Core loss measurements at a ux density of 10kilogausses were taken for both annealed and unannealed magnetic samples. The core losses of the unannealed sample laminations are presented in Table I and the core losses of the annealed laminations are 'presented in Table 1I.

TABLE I (Watts Per Pound) at 10 Klogausses Minutes 1 50o 1550 1,600 1,650 ,700 1,750 1,8 ,550 ,900

5F. R F. 112. F. F. F.

10 2. 617 2. 633 2. ssa 2.637 2. 617 5 2. 671 2. 630 2. 655 2. 623 2.620 y 2% 2. 640 2. 613 2. 680 2. 610 2. 647 1 2. 637 2. 657 2. 657 2. 660 2. 647 1/6 2.607 2.657 2.643 2.667 2.643

TABLE II Average Core Losses of Single Strips After Anneaiing (Watts Per Pound) at 10 Kilogausses Minutes 1,500 1,5 1,600 1,650 1,700 ,750 1,800 1,a 1,900 F. F. F. F. F. F. F, aF. F.

A steel strip of the foregoing composition was given a tinal mill pass that produced a 4 percent elongation and another steel strip of the same' composition was given a mill pass that produced a l0 percent elongation. The final thickness of the steel strip having the 4 percent elongation was 24.8 mils and the nal thickness of the material having the l0ipe`rcent elongation was 23.6 mils. The two steel strips were cut into rectangularlaminations 4 inches long and 1%6 inch wide with the rolling direction parallel yto the 4 inch dimension. The fixedannealing times, used at each 50 degree temperature interval between 1500 degrees Fahrenheit to 1900 degrees Fahren-l heit, were 1/2, 1, 21/2 and 5 minutes. Three laminations were annealed at each combination of time and temperature and the laminations with the 4 percent and the 10 percent elongations were given identical annealing treat- Referring to FIG. 4, it will be noted that the reduction of core loss of the sample laminations annealed in accordance with the present invention reach a peak or minimum core loss and then decrease. From these curves, it can be readily seen that sample laminations which were annealed at lower temperatures require longer times to reach their minimum core loss level, while those annealed at higher temperatures require shorter annealing times to reach approximately the same level. According to the present invention, the preferred times and temperatures for annealing the 3.06 percent silicon steel strip used in this exemplitcation of the invention are as follows.

Temperature by Time required degrees Fahrenheit: (minutes) er than 4 percent. It will be appreciated that the annealing times given in FlG. 4 are minimum times at an isovness of the strip and'method of heating, sufficient time must be allowed for the entire mass to come up to temperature before the specified times apply.

In carrying out the foregoing investigations of the effect of the various factors on the annealing time, it was found that for a fixed annealing time the lowest temperature which produced a 100 percent grain response also produced the largest grains and the lowest core loss obtainable for such an annealing time. Annealing at a higher temperature than required for a given annealing time also produced a 100 percent response but the grains became smaller and the core loss increased. In other words,'1 have found that minimum core loss is achieved at approximately the same time that a 100 percent grain response is initially obtained.

In the curves ofFIG. 5 the relationship between percent grain response and temperature at fixed annealing times is graphically shown for a 1.5 percent silicon steel. In the curve of FIG. 6 the diameter of the average grain size in millimeters is plotted against annealing temperature. The 1.5 percent silicon steel strip used to obtain the data for the curves in FIGS. 5 and 6 was given a final mill pass to produce approximately a 4 percent elongation andl was cut in rectangular laminations 111/32 inches long and 1?/16 inches Wide. The final gauge of the strip was .025 inch. The samplev laminations were heated at temperatures of 1600, 1700, 1750, 1800, 1850 and 1900 degrees Fahrenheit for a time interval at each temperature of l5 seconds, 30 seconds, 1 minute, 5 minutes, 15 minutes, 30 minutes and 60 minutes. After each treatment, the sample laminations were air cooled to room temperature, washed clean with water and macroetched in a 30 percent nitric acid solution. The percent area covered by large grains was ascertained by visual inspection and the average grain size of the grains was measured across their average diameter.

' From the curves of FIG. 5 it will be seen that a 100 percent grain response or minimum core loss can be obtained by magnetically annealing the 1.5 percent silicon steel strip having a 4 percent elongation at the following times of temperatures.

Temperature by degrees Fahrenheit: Time required It will be appreciated that the short magnetic annealing times required in accordance with the present inven- 'tion make it possible for the fabricated electric parts to be heated by high frequency induction methods in a product-ion line type of operation and is the preferred method of heating. If flame heating is to be used or if it is to be carried out by passing the material through a conventional furnace, it is. necessary to maintainv a 'small number of layers as the parts formed of the strip are continuously fed to the heating means." The parts should not be very far removed from an outer surface of the layers so that the heat can effectively penetrate all the parts. High frequency induction heating is preferred thermal annealing temperature. Depending on the thick- 8 decrease. The decrease in grain size from the 15 minute time interval to the 15 second time interval is relatively small for the 1.5 percent silicon steel. It was found for this steel that a temperature of 1850 degrees Fahrenheit and a magnetic annealing time of l minute produced uniformly improved magnetic properties since the time interval could be accurately controlled.

The' exact mechanism of the magnetic annealing treatment of the present invention is not clearly understood", t by but is based on strain induced grain boundary migration. The outstanding factor of the mechanism is that abnormal grain size is obtained in comparatively short periods of time. It is clear that conventional steels would require extremely long periods of time and temperature to produce the magnetic properties achieved by the anneal of this invention. It is believed that the final grain size .is dependent tota large extent upon the number of active growth sites which are nucleated. The annealing treatment, all other factors being equal, does not depend upon additional grain growth following complete grain response as in the case of normal recrystallization. The extremely fast rate of abnormal grain growth can be attributed to the fact that the growing grains, prior to the 100 percent grain response are consuming a relatively fine grained high energy matrix. Such a mechanism differs from the grain growth that takes place in acompletely recrystallized structure in which a substantially lesser driving force is available for the reaction because of the greater uniformity of the grain size and greater equality of the energy levels.

While this invention has been explained by describing several exemplifications thereof, it will be apparent that improvements and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Pa'tent of the United States is:

1. A process of treating silicon strip steel having a silicon content between 0.25 percent and 3.5 percent and hot rolled to a thickness between .05 and .125 inch, Vsaid process comprising the steps of: cold rolling said strip to an intermediate thickness which when reduced to final gauge will produce a predetermined elongation between 2 and 12 percent in the strip, heating said strip at a normalizing temperature for a period sufficient to effect recrystallization without appreciable grain growth, cold rolling said strip to final gauge, and annealing said strip at a temperature ranging from 1650 to 2100 degrees Fahrenheit for a predetermined period of time ranging from l5 seconds to 15 minutes at a temperature which will produce a minimum core loss for said predetermined period of time and said predetermined elongation, increasing said elongation causing a decrease in the annealing temperature required to produce said minimum core loss.

2. A process of treating a strip steel hot rolled to a thickness ranging from .05 to .125 inch and having a silicon content between 0.25 percent and 3.5 percent, said process comprising: cold rolling said strip to an intermediate thickness requiring a predetermined elongation from 2 to l2 percent to reduce said thickness to final gauge, heating said strip at a normalizing temperature for a sufficient period of time to effect recrystallization without any appreciable grain growth, cooling said strip, cold rolling said strip to final gauge and heating said strip at a temperature ranging from 1650 to 2100 degrees Fahrenheit for a preselected period of time ranging from 15 seconds to l5 minutes at the since such heating results in the generation of heat from lowest temperature required to produce a minimum core within the part and thereby quickly brings the material up to the required temperature.

Referring now to FIG. 6, it will be seen that as the temperature increases and the time required for a 100 loss for said preselected period of time and said predetermined elongation, increasing said elongation causing a decrease in the annealing temperature required to produce said minimum core loss.

percent grain response decreases, the grain size will also 3. A process of treating a silicon steel strip hot rolled to a thickness ranging from .05 to .125 inch `and having a silicon content between 0.25 percent and 3.5 Apercent comprising the steps of: cold rolling said strip to an intermediate thickness requiring a predetermined elongation ranging from 2 to 12 percentto reduce said thickness to final gauge, heating said strip at a normalizing temperature for a period long enough to etect recrystal- .lization without any appreciable grain growth, cooling said strip, cold rolling said strip to final gauge, andannealing said strip at a temperature ranging from 1650 to 2100 degrees Fahrenheit for a preselected period 'of time ranging from 15 seconds to 15 minutes at approxi-r mately the lowest temperature required to produce a minimum core loss corresponding to said preselected period of time and said predetermined elongation, increasing said elongation causing a decrease in the annealing temperature required to produce said minimum core loss.

4. A 'process of treating silicon strip steel hot rolled to a thickness ranging between .05 and .125 inch and having a silicon content from 0.25 to 3.5 percent comprising the steps of: cold rolling said strip to an intermediate thickness requiring approximately 10 percent to effect recrystallization without appreciable grain growth elongation to reduce said strip to final gauge, heating 25 and then cooling said strip, cold-` rolling said strip to' final gauge, and annealing said strip for approximately l minute at a temperature ranging from 1650 to 1850 degrees Fahrenheit that will produce a minimum core loss corresponding to said elongation and said annealing period, increasing said elongation causing a decrease in the annealing temperature required to produce minimum core loss.

References Cited in the le of this patent UNITED sTATEs PATENTS 2,287,467 Carpenter et al. June 23, 1942 2,378,321 Pakkala June 12, 1945 2,738,295 McKnight et al, Mar. 13, 1956 2,867,558 May Jan. 6, 1959 OTHER REFERENCES Engineering Metals and Their Alloys, Samans, The Macmillan Co., N Y., 1949 (pp. v92-94 relied upon).

A Dictionary of Metallurgy, A. D. Merriman, Mao- Donald & Evans, Ltd., London 1958 (p. 174 relied upon). l 

1. A PROCESS OF TREATING SILICON STRIP STEEL HAVING A SILICON CONTENT BETWEEN 0.25 PERCENT AND 3.5 PERCENT AND HOT ROLLED TO A THICKNESS BETWEEN .05 AND 1.25 INCH, SAID PROCESS COMPRISING THE STEPS OF: COLD ROOLING SAID STRIP TO AN INTERMEDIATE THICKNESS WHICH WHEN REDUCED TO FINAL GAUGE WILL PRODUCE A PREDETERMINED ELONGATION BETWEEN 2 AND 12 PERCENT IN THE STRIP, HEATING SAID STRIP AT A NORMALIZING TEMPERATURE FOR A PERIOD SUFFICIENT TO EFFECT RECRYSTALLIZATION WITHOUT APPRECIABLE GRAIN GROWTH, COLD ROLLING SAID STRIP TO FINAL GAUGE, AND ANNEALING SAID STRIP AT A TEMPERATURE RANGING FROM 1650 TO 2100 DEGREES FAHRENHEIT FOR A PREDETERMINED PERIOD OF TIME RANGING FROM 15 SECONDS TO 15 MINUTES AT A TEMPERATURE WHICH WILL PRODUCE A MINIMUM CORE LOSS FOR SAID PREDETERMINED PERIOD OF TIME AND SAID PREDETERMINED ELONGATION, INCREASING SAID ELONGATION CAUSING A DECREASE IN THE ANNEALING TEMPERATURE REQUIRED TO PRODUCE SAID MINIMUM CORE LOSS. 